The present invention relates to a combined circuit arrangement wherein a plurality of electronic components are associated with a substrate body.
A circuit arrangement of this type is known from German OS No. 21 20 787, incorporated herein by reference. An integrated circuit is described there consisting of active and passive components exhibiting layers of doping materials for generating active components and conductive contacts, and also exhibiting layers of substances which form insulating layers on the surface of a semiconductor substrate body.
Further layers which can be employed as tracks, resistors, or capacitors can be applied to such an insulating layer. For manufacturing such a circuit arrangement the semiconductor substrate body is provided as a shared substrate body for the active and passive components and screen printing is employed. It is also specified there to apply glasses by means of screen printing, these being placed in their conductive state and back to their initial state by means of a current or voltage surge. Such a glass layer is employed as the source for doping elements for doping diffusions to be performed.
It is known to provide over-voltage devices on circuits--preferably semiconductor circuits--for protection against over-voltages. Thyristors which can be electrically connected to leads of respective circuits are particularly suitable for this purpose.
Varistors are preferably components consisting of doped zinc oxide ceramic having electrodes situated at or on the ceramic body (See U.S. Pat. No. 3,805,114, incorporated herein by reference). Given a low voltage thereacross, a varistor exhibits high-resistance behavior and only exhibits a lower resistance given a higher voltage. With such a component, current I and voltage U depend upon one another according to the equation I=(U/K) .alpha., where K is a material constant and .alpha. is the coefficient of non-linearity. A zinc oxide ceramic body of a varistor can have the electrical varistor property throughout. Also known, however, are varistors wherein only a layer region of the zinc oxide ceramic body exhibits the varistor property (See German OS No. 28 20 118 and German OS No. 29 21 497, both incorporated herein by reference). The zinc oxide of the remaining part of the ceramic body of such a varistor is always a low-resistance independent of voltage.
A voltage-independent, low-resistance zinc oxide ceramic body is first manufactured by means of mixing starting materials, grinding the slip or mixture, compressing into molded bodies, and sintering the molded bodies. The varistor property is then subsequently achieved by means of in-diffusion of one or more of the doping substances such as, for example, bismuth oxide, boron oxide, cobalt oxide, antimony oxide, chrome oxide, titanium oxide, praseodymium oxide, calcium oxide and other substances.
In conjunction with the employment of circuits which for example are pure semiconductor circuits, hybrid circuits and/or circuits of a different structure, the object is always to achieve over-voltage protection with a structure as low in inductance as possible given the smallest possible space requirement. Inductive portions of the over-voltage protection lead to a reduction of the protective effect given over-voltages having a high rise rate. Furthermore, a respective new circuit arrangement should be manufacturable with the technological means and methods which have already been previously employed and for which the production plants have been equipped.